A severe or chronic total occlusion (CTO) is a vessel blockage that prevents blood flow beyond the occlusion. Chronic total occlusions most often occur in coronary and peripheral arteries and result from atherosclerosis.
A common procedure for treating CTOs is percutaneous transluminal angioplasty. During an angioplasty procedure, access to a desired blood vessel is obtained and a guidewire is introduced into the blood vessel in an antegrade direction. The guidewire is maneuvered into place, including being passed into and through the occlusion, and acts as a guide for positioning subsequent treatment devices (e.g., a balloon catheter and/or a stent catheter) over-the-wire. The guiding function of the guidewire can reduce the risk of vessel trauma (e.g., scraping of a luminal wall at an undesired angle or vessel perforation) by the less flexible and larger diameter treatment devices during advancement.
A failure mode for angioplasty is the inability to successful pass a guidewire through an occlusion and into the true lumen of the blood vessel distal to the occlusion. The occlusion may be composed of dense plaque having a proximal cap that prevents penetration by the guidewire.